Plot two histograms in the same graph

Kaedah 1:

hist(x)
hist(y, add=TRUE)

(Di ambil dari rujukan 2, bahagian komen)

Kaedah 2:

Sila rujuk rujukan nombor 2 dan 3.

Rujukan:

1. http://r.789695.n4.nabble.com/two-histograms-in-the-same-graph-td846587.html
2. http://onertipaday.blogspot.com/2007/04/how-to-superimpose-histograms.html
3. http://onertipaday.blogspot.com/2007/05/multiple-histograms-in-one-plot.html